zita-lrx - 4th order crossover filters

Zita-lrx is a command line jack application providing 2, 3, or 4-band,
4th order crossover filters. The filter type is continuously variable
between Linkwitz-Riley (-6dB at the xover frequency) and Butterworth
(-3 dB at the xover frequency). Outputs are exactly phase matched in
the crossover regions.